1. Field of the Invention
This invention pertains generally to devices that assist with internal diagnostic imaging and treatment procedures, and more particularly to a catheter based balloon for temperature, acoustical and radiological blocking as well as the repositioning of treated and sensitive tissues.
2. Description of Related Art
Conventional hyperthermia or tissue heating at moderate temperatures (41° C. to 45° C.) has been shown to promote changes in cellular dynamics, tumor microcirculation, and blood vessel permeability that can be exploited to enhance other therapies such as radiation and chemotherapy for cancer treatment, drug delivery and potentiation, gene therapy, and even organ preservation.
The immediate physiological effects of thermal exposure during thermal therapies include heat-induced acceleration of metabolism, thermal inactivation of enzymes, and the rupture of cell membranes. Delayed effects of thermal exposure include intracellular and tissue edema, hyperemia with increasing blood flow, as well as an increase in blood vessel permeability and dilatation.
The damage due to thermal effects alone is reversible for thermal exposures at lower temperatures with relatively shorter times of exposure (non-lethal thermal doses). For exposures at comparatively longer times or higher temperatures, cellular repair mechanisms can no longer keep up or lose function due to the thermal damage of key enzymes, and cell death and tissue necrosis will occur within 3 to 5 days. Different tissues exhibit different levels of sensitivity to thermal damage.
The localization of exposure of high-temperature hyperthermia at temperatures greater than 45° C. to 50° C. can be used to selectively destroy or permanently alter tissue regions. In the high-temperature regime, thermal coagulation and thermal necrosis occurs in tissues exposed to temperatures greater than 50° C. to 55° C. for a duration of 1 to 2 minutes or shorter times at even higher temperatures. The thermal exposure of tissues to high temperatures causes many cellular and tissue structural proteins to undergo irreversible denaturation and conformational changes. These thermal effects are lethal and immediate, producing thermally coagulated (dead) tissue.
On the extreme end, temperatures close to or greater than 100° C. generate less subtle effects, such as explosive vaporization and ablation of tissue. Varying degrees of high temperature thermal therapy are used for cancer therapy, treatment of cardiac arrhythmias, treatment of benign disease (BPH, uterine and breast fibroids), snoring, cosmesis, tissue modification, treatment of sports injuries, etc. However, the efficacy of these treatment modalities may be limited due to inadequacy in protecting sensitive non-targeted tissues or adequately treating a large enough of a volume of tissue.
One example of an organ that responds well to various forms of thermal therapy is the prostate gland. Benign prostatic hyperplasia (BPH) is a frequent benign disease that often requires surgical intervention. Prostate cancer affects 250,000 men annually. Surgery and radiation therapy are the common forms of treatment for prostate cancer. Numerous biological and clinical investigations have demonstrated that heat treatments within the 41° C. to 45° C. range can significantly enhance clinical responses to radiation therapy, and has the potential for enhancing other therapies such as chemotherapy, immunotherapy, and gene therapy as well.
Furthermore, high temperature hyperthermia (greater than 50° C.) alone may be used for selective tissue destruction as an alternative to conventional invasive surgery (Transurethral Resection, or TURP). Thermal techniques can also be utilized to complement existing courses of treatment or provide a minimally invasive alternative to surgery with less complications, and morbidity for each of these diseases. Additionally, transurethral, transrectal, and interstitial systems that use RF currents, lasers, microwaves, ultrasound, and thermal conduction heating technology, can be implemented in the clinic or under development for this type of therapy.
Presently, treating the prostate gland with heat is problematic. The most significant clinical experience to date includes treatment of BPH with transurethral microwave devices. If properly positioned within the prostatic urethra, these devices can thermally destroy a region within the center of the prostate, which leads to a reduction of BPH symptoms. Improvements to these devices and clinical protocols are directed towards decreasing treatment time and destroying larger amounts of tissue in a more precise manner. Although moderately effective for treatment of BPH, these devices are not effective for treating prostate cancer, which mostly involves tissues away from the urethra in the posterior portion of the gland, often adjacent to critical nerves and the rectum. In order to treat large distances from the urethra, higher amounts of energy and greater temperatures are required, leading to damage of the rectum or surrounding non-targeted tissues. Precise techniques for localizing or depositing energy within the gland are required for the treatment of cancer. Transrectal focused ultrasound devices (HIFU) offer some spatial control but treating the most dorsal portion of the prostate is still problematic, due to the risk of thermal damage to the rectum. New developments in transurethral ultrasound heating technology have demonstrated precise, directed and extensive heating capabilities in the anterior and lateral prostate tissue. Large volumes of tissue can be heated in the posterior margin of the prostate gland, but extreme care needs to be undertaken to avoid damage to the rectum and other non-target tissues. The potential exists to heat the entire prostate with transurethral ultrasound if the rectum tissue can be protected and incident energy can be reflected back to the prostate. Interstitial approaches (needle implantation) provide another method of localizing heating energy, but only interstitial ultrasound has the capability of directional heating patterns to avoid the rectum and surrounding bone.
A second example of effective thermal therapy is in the treatment of gynecological diseases. Gynecological diseases treated by thermal therapy typically include menorrhagia, uterine and cervical cancer, and uterine fibroids. In the case of menorrhagia, different heating modalities are placed directly within the os of the uterus and heating energy is applied. For fibroids, interstitial lasers and RF energy have been applied to thermally destroy the tissues. New developments in ultrasound heating technology are also leading to external, intracavitary, and interstitial techniques that promise better localization. The amount of heating power, temperature distributions, and applicator placement are often limited in the treatment of these diseases by the need to protect sensitive non-targeted tissues.
Thus it can be seen that the usefulness and efficacy of thermal therapies are limited by the sensitivity to thermal exposure of associated non-target tissues. The usefulness and efficacy of treatments other than thermal therapy, such as interstitial and external beam radiation therapies, may also be limited by the collateral damage to non-target tissues that can occur with these therapies.
Some other cancer therapies include the placement of small radiation sources into the tumor using specialized catheters in a procedure called brachytherapy. For example, low dose rate brachytherapy (LDR) includes the permanent implantation of radioactive “seeds” of gold or iodine into the tumor or organ tissues. The implanted seeds give off radiation in low doses over a period of several months and remain in the organ permanently. A typical LDR brachytherapy procedure for prostate cancer may include the placement of over 100 radioactive implants in the prostate gland of the patient.
A second brachytherapy procedure was developed, known as high dose rate brachytherapy (HDR), which uses precisely positioned catheters at tumor sites. High dose radiation sources are then sent to the tumor sites through the catheters and removed from the body after a period of time and are temporary implants. Thus, a high dose of radiation can be directed to the cancerous tumor for a time and removed. However, proper placement of the HDR catheters is critical because of the high dosages of radiation involved.
Prostate adenocarcinomas for example, are particularly well suited for both LDR and HDR brachytherapy procedures. The three dimensional visualization of the placement of 125-Iodide seeds during transperperineal implantation, for example, has recently been accomplished with the use of transrectal ultrasonography (“TRUS”). Unfortunately, the imprecise placement of radiation sources can still occur with the use of ultrasound due to the proximity of the bladder and rectum and associated structures to the prostate gland. For both of these forms of interstitial radiation therapy, computer treatment planning is performed to produce a specific radiation dose distribution encompassing the target regions, and includes a safety margin around sensitive structures such as the rectum. For many cases, especially treatment of a previously radiated recurrence, the total radiation dose that can be applied is limited due to the exposure limits on normal tissue structures that are close to the prostate gland such as the rectum, bladder and urethra. For prostate and uterine tissue, this translates to a limited radiation treatment in the posterior portion of the organ in proximity to the rectum.
Accordingly, there is a continuing need in the art for a device or procedure that can apply thermal or radiation therapy to the target tissue or tumor while insulating or positioning associated sensitive structures to modify exposure to radiation or thermal treatments and enhancing diagnostic imaging. The present invention satisfies these needs, as well as others, and generally overcomes the deficiencies found in existing equipment and methods.